The invention concerns a magnetic valve controlled injection device consisting of pump and nozzle for air compression internal combustion engines having a mounting hole means for a fuel pump casing in the cylinder head of the engine wherein there is a pump piston, displaced longitudinally in the pump casing and driven by a camshaft, supported from the cylinder head, via a drive element, and which pump piston shuts off an inlet in the pump working space and wherein a pressure conduit starting from the pump working space--leads to the fuel nozzle and to a magnetic valve controlling the beginning of the pumping and the end of pumping as a function of operating parameters of the internal combustion engine.
A magnetic-valve-controlled injection device of this type is known from GB 21 31 873 A. The pump and nozzle, combined to form a structural unit in this case--generally referred to as pump-nozzle--and the magnetic valve is not easily serviceable because it is necessary to remove the complete structural unit during a nozzle change or pump change. In addition, removal is even more difficult because of the positioning of the cam drive. The pump is fixed over the nozzle. There are high mechanical and hydraulic loads.
An object of the invention is to remove the disadvantages present in this magnetic valve controlled injection device consisting of pump and nozzle and, in addition, to make possible a compact, simple and service friendly structure by means of a special arrangement of pump, nozzle and magnetic valve, this structure ensuring continuous and troublefree operation.
The object is obtained by having a magnetic valve form a structural unit jointly with the fuel pump or fuel nozzle and with a mounting hole being provided in the cylinder head for the fuel pump so that the pump is located separately from the nozzle and is connected to the nozzle by a relatively short exposed pressure pipe and furthermore, that the pump is so mounted that there is no hindrance on the camshaft side for removal of the pump and further that the fuel nozzle is independently fastened to the cylinder head so that it can be removed towards the outside. Additionally, a casing part of the pump, which faces away from a drive element of the pump, and the magnetic valve, which controls the beginning and ending of pumping as a function of operating parameters of the engine, are both located outside the space enclosed by the cylinder head and a cylinder head cover.
These measures according to the invention provide easy accessibility to the injection system. The structural separation of pump and nozzle permits a flat structure and make possible, in a simple and rapid manner, installation and removal of only the structural unit consisting of the nozzle and the magnetic valve, or the pump and the magnetic valve. In addition, installation and removal of the magnetic valve separate from the nozzle or the pump is possible. Because of the special position of the magnetic valve, namely outside the engine oil space, this magnetic valve is subject to substantially smaller thermal loads. Complicated sealing arrangements for the electrical connections are unnecessary.
An injection device with mechanical control consisting of pump and nozzle (Guenter Elsbett, "Das integrierte Kraftstoffeinspritzsystem fuer Direkteinspritz-Dieselmotoren", XIX International Fisita Congress, 8.-12. Nov. 1982, Paper 82029) is known in which the pump does, in fact, have a separate position from the nozzle, but in which there is a complicated mechanical control for both the beginning of pumping and for the quantity of fluid delivered. Because of this, control rods have to bridge the complete length of the cylinder head. The transmission of the stroke motion of the pump piston takes place by means of an intermediate piece which is supported rotatably in a threaded insert in order to permit a change of length of the pump tappet for the purpose of controlling the beginning of pumping. The adjustment principle is complicated and the pump drive can only be dismantled after the removal of the camshaft.
An advantage is obtained by having the fuel pump located at one side of and within a height determined by the length of the fuel nozzle.
Another advantage is obtained by having the fuel pump driven by a longitudinally displaceable roller tappet or alternatively a roller rocker arm.
It is also advantageous to have the fuel pump and magnetic valve as a single unit with a single mounting hole in the cylinder head.
Also a cover can be provided which will act as a wall boundary for a low pressure space in the fuel pump assembly. This space can be connected intermediate the two ends of the fuel pressure pipe leading from the fuel supply to the fuel return. Also advantageous is having a low pressure chamber connector to the conduit leading to the magnetic control valve and thus controlled thereby.
Also advantageous is the fact that the inlet and outlet to the magnetic valve can be reversed in some institutions.
Because the high pressure side of the fuel pipework system is located outside the cylinder head, it is no longer possible for the engine oil to be diluted by fuel entering it. The pressure space on the low pressure side, in its function as pressure wave damper, is also not located in the cylinder head, but rather in the pump casing located outside the cylinder head, so that lower fuel temperature are obtained. Because of the arrangement of the low pressure chamber immediately at the magnetic valve, pressure fluctuations occurring when the magnetic valve is opened are avoided.
These and other objects, features, and advantaged of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which shows, for the purposes of illustration only, plural embodiments in accordance with the present invention, and wherein: